Understanding the role and significance of the Arctic for the cycling and fate of persistent organic pollutants (ARCPOP)

2006年6月15日，世界野生动物联合会(WWF)发布了一份名为《悄悄杀死它们》的报告，其中强调了人们对北极野生动物，特别是北极熊等海洋哺乳动物中持久性有机污染物的积累和毒性影响的担忧。《泰晤士报》用了一整页的篇幅总结了这份报告，并详细介绍了滴滴涕和多氯联苯(PCBS)等“遗留”化学物质，以及溴化阻燃剂和全氟表面活性剂等“新”化学污染物的增加，这些污染物也在北极动物中积累，增加了额外的毒性风险。这些污染物的高水平正在降低北极熊等动物在严酷的北极条件下生存和应对气候变化影响的能力。这项提案中的工作旨在研究这些化学品如何被运送到北冰洋的表层水域，从而成为海洋食物网的基础。持久性有机污染物通过长距离运输进入北极，主要通过来自欧洲、北美和亚洲来源地区的空气，但也通过表层洋流进入北极。北极的寒冷条件有助于促进这些化学物质在雪和地表水中的积累，并减缓任何分解和蒸发损失。然而，人们对从大气中去除这些污染物，将其储存在冰雪中，然后将其转移到北冰洋的过程知之甚少，但这些过程可能会因所涉及的化学物质而有所不同。例如，一些化学品非常易挥发(即它们有蒸发的趋势)，因此，尽管它们可以到达北极并在降雪时沉积，但由于在北极夏季将其OSS返回大气，它们不太可能到达海洋。另一方面，较重、挥发性较低的化学物质会与雪和颗粒强烈结合，并在夏季融化期间被输送到海水中。气候变化和世界变暖正在改变北极，影响污染物的传播途径。例如，冰铅的数量正在增加(海冰上的大裂缝，形成海水的“湖”)。因此，化学污染物到达海水的路径正在发生变化，实际上可能会变得更短，对海洋生物构成更大的威胁。在无冰期间，海洋表面的水与大气接触(而不是覆盖着海冰)，空气中的污染物可以直接溶解到寒冷的表面水域中。令人鼓舞的是，有证据表明，北极大气中的一些传统污染物正在减少，但许多现代的化学物质在北极生物群中实际上正在增加，需要进行工作来测量它们的输入，并了解它们在这种不寻常的环境中的行为。例如，在极地日出(24小时白天)后的阳光照射下的表面雪中，其中一些化合物可以通过吸收阳光来降解，在某些情况下，这可能会产生更稳定的化合物，随后进入食物链。因此，随着降雪而沉积的化学污染物的数量和融雪过程中化学污染物的去向是需要解决的重要过程，特别是要了解这些污染物对海洋生态系统的负荷和影响。该项目旨在了解这些过程，并了解哪些类型的污染物及其数量对野生动物构成最大的威胁。

On June 15 2006, the World Wildlife Federation (WWF) released a report called 'Killing them Softly', which highlighted concern over the accumulation and toxic effects of persistent organic pollutants present in Arctic wildlife, particularly marine mammals such as the Polar Bear. The Times newspaper ran a full-page article summarising this report and detailed 'legacy' chemicals such as DDT and polychlorinated biphenyls (PCBs), as well as the rise in 'new' chemical contaminants such as brominated flame retardents and perfluorinated surfactants, which are also accumulating in arctic fauna and adding an additional toxic risk. The high levels of these contaminants are making animals like the Polar Bear less capable of surviving the harsh Arctic conditions and dealing with the impacts of climate change. The work in this proposal intends to examine how these chemicals are delivered to surface waters of the Arctic Ocean, and hence the base of the marine foodweb. Persistent organic pollutants reach the Arctic via long-range transport, primarily through the air from source regions in Europe, North America and Asia, but also with surface ocean currents. The cold conditions of the Arctic help to promote the accumulation of these chemicals in snow and surface waters and slows any breakdown and evaporative loss. However, the processes that remove these pollutants from the atmosphere, store them in snow and ice and then transfer them to the Arctic Ocean are poorly understood, and yet these processes may differ depending on the chemcial in question. For example, some chemicals are rather volatile (i.e. they have a tendency to evaporate), so while they can reach the Arctic and be deposited with snowfall they are unlikely to reach the ocean due to ltheir oss back to the atmosphere during the arctic summer. On the other hand, heavier, less volatile chemicals, become strongly bound to snow and particles and can be delivered to seawater during summer melt. Climate change and a warmer world are altering the Arctic and affecting pollutant pathways. For example, the number of ice-leads (large cracks in the sea-ice that give rise to 'lakes' of seawater) are increasing. As a result, the pathways that chemical pollutants take to reach ocean waters are changing and may actually be made shorter, posing an even greater threat to marine wildlife. During ice-free periods, the ocean surface water is in contact with the atmosphere (rather than capped with sea-ice) and airborne pollutants can dissolve directly into cold surface waters. Encouragingly, there is evidence that some of the 'legacy' pollutants are declining in the arctic atmosphere, but many 'modern' chemicals are actually increasing in arctic biota and work is required to measure their input and understand their behaviour in this unusual environment. For example, in sunlit surface snow following polar sunrise (24 h daylight), some of these compounds can degrade by absorbing the sunlight, and in some cases, this can give rise to more stable compounds that subsequently enter the foodchain. Therefore, the quantity of chemical pollutant that is deposited with snowfall and the chemical's fate during snowmelt are important processes to address, especially to understand the loading and impact of these pollutants on the marine ecosystem. This project aims to understand these processes, and to understand which type of pollutants and their quantities pose the greatest threat to wildlife.